hashtable in js

hashtable.js

var HashTable = function (key) {
  this.store = {};
  this.key = key;
};

HashTable.prototype = {
  getItem : function (key) {
    return this.store[key];
  },
  pushItem : function (item) {
    this.store[item[this.key]] = item;
  },
  get : function (){
    return this.store;
  },
  add : function (data) {
    var _this = this;
    if (Array.isArray(data)) {
      data.forEach(function (item) {
        _this.pushItem(item);
      });
    } else {
      this.pushItem(data);
    }
    return this.store;
  },
  destroy : function () {
    this.store = {};
    return this.store;
  }
};

var booksHash = new HashTable('id');